NUMERICAL INVESTIGATION ON FLOW GENERATED BY INVENT MIXER IN FULL-SCALE WASTEWATER STIRRED TANK

This paper investigates behaviors of three dimensional, full-scale flows generated by the newly developed INVENT HyperClassic (R) mixers in a primary influent channel of a wastewater treatment plant in the New York City. The ANSYS FLUENT, in conjunction with the standard k-epsilon turbulence closure and a multiple reference frame model, is employed for the investigations. Numerical simulations reveal large-scale circulations on cross sections perpendicular to the channel direction as a main feature of the flows, and such circulations are expected to be a key mechanism to enhance their mixing and keep solid particles in suspension. Stronger turbulence mixing in terms of turbulence kinetic energy and dissipation rate and more intensive mixing in the sense of time average and evaluated by the Lyapunov exponent are observed in the presence of two mixers than those with a single mixer. Additionally, a larger inlet velocity of the channel results in an increase in turbulence kinetic energy and dissipation rate but not necessarily a growth of the Lyapunov exponent.